252 THE ILLINOIS GLACIAL LOBE. 



among which are sags and shallow basins. The swells are usually closely 

 aggregated, but in places nearly plane tracts of a square mile or more 

 appear in the midst of this belt. An instance of such a plane tract may 

 be seen south of Deer Creek village. The elevated tract on the northeast 

 border of this moraine has only occasional low swells 10 or 15 feet in 

 height, the greater part of the surface being- as smooth as the plains farther 

 north and east, and differing from them only 50 to 75 feet in altitude. The 

 descent is made in a distance of 2 or 3 miles, and is therefore so gradual as 

 to be scarcely perceptible to the eye. The relief on the outer border is 

 more conspicuous than on the inner, a rise of 100 feet being' made in about 

 2 miles at the prominent parts of the moraine. This border is also made 

 conspicuous by the change from the very flat surface outside the moraine 

 to the billowy surface presented by its outer face. 



Between Mackinaw River and the Ford County reentrant. East of the MackiliaW Rivei*, 



near the borders of Woodford, McLean, and Tazewell counties, the Bloom- 

 ington morainic system presents two well-defined bulky ridges which are 

 separated by a narrow plain or sag 1 or 2 miles or more in width. These 

 ridg-es are distinctly maintained from the extreme northwest corner of 

 McLean County eastward to Padua, a distance of nearly 30 miles, beyond 

 which, for 20 to 25 miles, to the Ford County reentrant, they are combined 

 into a single belt. 



The inner ridge enters McLean County from Woodford County near 

 the line of the third principal meridian and passes southeastward through 

 Normal and thence eastward through Barnes to Padua, where it becomes 

 combined with the outer ridge. It has a general width of 2 or 3 miles and 

 rises 30 to 50 feet above the sag or plain on its south border. The surface 

 is billowy, with oscillations of 20 or 30 feet between the higher swells and 

 neighboring sag's. Many smaller swells occur, with a height of 5 or 10 

 feet. The slope of these swells is usually gentle, and knolls 20 feet in 

 height occupy several acres. In places this moraine presents a sharply 

 outlined crest; a conspicuous instance was noted northwest of Padua, where 

 a ridge-like crest with a width of only one-fourth to one-half mile stands 

 about 50 feet above the tracts on either side. As a rule, however, the 

 higher portion of this belt consist* of a series of swells similar to those found 

 on the slopes. For several miles north from this inner ridge the surface is 



